Activation

Activation in Firebug Terminology means enabling its modules, so they start processing the data of a specific website. Firebug supports different activation models. These models were improved over time. The biggest change happened in Firebug 1.4.

Contents

The default behavior is to enable Firebug per URL. This means that if you open Firebug via F12 or by clicking its Start Button being at a website, the next time you visit the same website the Firebug window will be opened again.
It thereby follows the same origin policy. (Note that there was one exception in regard of subdomains not being treated differently. This was fixed in Firebug 1.11.)

There's a preferenceActivate Same Origin URLs to control whether the activation should follow the same origin policy. If this option is disabled, Firebug will disregard the origin when deciding to activate or not, i.e. Firebug can be activated for each URL path individually disregarding parameters and anchors.

Besides the general activation of Firebug there are also some panels, which allow to enable/disable them. The reason for disabling single panels is to avoid wasting system resources for things you don't need. E.g. as a web designer you probably won't need the Net Panel functionality.

The panel activation model currently only supports an on/off state. I.e. if you enable the Script Panel, it will subsequently be enabled for all sites Firebug is activated for.